Which of the following two sentences is correct?
a) Which of the two boxes is preferable ?
b) Which of the two boxes is more preferred?
I think it should be a) because Oxford dictionary online says preferable means:
More desirable or suitable:
While it would be preferable if the Complainant did so, it is incorrect to imply that only he can do this.
Moreover, from other sources of internet I get that preferred is used as favourite as in “my preferred site is StackExchange”.
So, more preferred is not making any sense to me.
However, the mostly reliable answer key points that the correct answer is b)! So I am confused and need your guidance.